1. Field of the Invention
The invention relates to novel bleach catalysts, compositions containing same and the method for using these catalysts in detergent compositions, especially for cleaning fabrics and dishes.
2. The Related Art
Many household and personal care products are formulated with an active oxygen-releasing material to effect removal of stain and soil. Oxygen-releasing materials have an important limitation; their activity is extremely temperature dependent. Temperatures in excess of 60.degree. C. are normally required to achieve any bleach effectiveness in an aqueous wash system. Especially for cleaning fabrics, high temperature operation is both economically and practically disadvantageous.
The art has partially solved the aforementioned problem through the use of activators. These activators, also known as bleach precursors, often appear in the form of carboxylic acid esters. In an aqueous liquor, anions of hydrogen peroxide react with the ester to generate the corresponding peroxyacid which oxidizes the stained substrate. Commercial application of this technology is found in certain fabric bleaching detergent powders incorporating sodium nonanoyloxybenzene sulfonate. This activator is typical of a class that features a phenol sulfonate leaving group; see U.S. Pat. No. 4,412,934 (Chung et al).
While carboxylic acid ester activators and the like are often effective, they are not catalytic. Once the ester has been perhydrolyzed, it can no longer be recycled. Accordingly, relatively large amounts of activator are necessary. Amounts as high as 8% may be necessary in a detergent formulation for bleaching fabrics. Cost for these relatively expensive activators is of major concern at such levels.
Outside the context of consumer products, there have been reports of catalytic oxidizing agents. F. A. Davis and coworkers, in a series of articles, reported preparation of a new class of stable oxidizing agents, namely 2-arenesulfonyl-3-aryloxaziridines. See Davis, Nadir and Gluger, J. C. S. Chem. Comm. 1977, 25; Davis, Lamendola Jr., Nadir, Kluger, Sederjarn, Panunto, Billmers, Jenkins Jr., Turchi, Watson, Chen and Kimura, J. Amer. Chem. Soc. 1980, 102, 2000; and Davis, Chattopadhay, Towson, Lal and Reedy, J. Org. Chem. 1988, 53, 2087. These oxaziridines were prepared by peracid or monopersulfate oxidation of a corresponding sulfonimine under alkaline conditions. In late 1988, Davis published a paper entitled "Selective Catalytic Oxidation of Sulfides to Sulfoxides Using N-sulfonyloxaziridines", J. Org. Chem, 1988, 53, 5004. Therein described is a system where sulfonimine reacts with monopersulfate to generate an in situ oxaziridine in a toluene-water biphasic mixture. Oxaziridine then coverts the sulfide to a sulfoxide and generates starting sulfonimine, thereby rendering the process catalytic in nature.
Sulfonimine chemistry has moved beyond the area of a mere synthetic tool. Recently, suifonimines have been recognized as useful for removing stains in consumer applications such as in the cleaning of fabrics. U.S. Pat. No. 5,041,232 (Batal et al) reports the bleaching activity of sulfonimines such as SULF-11 as effective at bleaching a variety of stains. During investigation of synthetic mutes to SULF-11, the present Applicants discovered certain reaction intermediates which by themselves exhibited catalytic bleaching activity.
Accordingly, it is an object of the present invention to provide novel bleach catalysts and detergent compositions containing such catalysts that operate over a wide temperature range including that of under 60.degree. C.
It is another object of the present invention to provide novel bleach catalysts which are effective at relatively low concentrations thereby achieving a cost-effective stain removal system.
It is a further object of the present invention to provide a method for bleaching stained substrates such as clothes, household hard surfaces including sinks, toilets and the like, and even dentures.
Other objects of the present invention will become more readily apparent through the following summary, detailed description and examples.